Breathing in the unfiltered air from busy traffic can shoot up passengers’ blood pressure. It doesn’t just happen during the drive; the effects stick around for up to 24 hours, say researchers.
For more than a hundred years, American cities have been crisscrossed by jam-packed roads. Highways and wide streets are now a big part of city life, with cars churning out pollution in nearby neighborhoods.
Bad for our health
Scientists are just starting to figure out how bad all that pollution is for our health. Breathing in the mix of exhaust fumes, particles from brakes and tires, and dust from the road during long-term exposure to traffic can lead to more heart problems, asthma, lung cancer, and even death.
“The body has a complex set of systems to try to keep blood pressure to your brain the same all the time. It’s a very complex, tightly regulated system, and it appears that somewhere, in one of those mechanisms, traffic-related air pollution interferes with blood pressure,” the researchers explain.
Researchers took healthy volunteers aged 22 to 45 on drives through Seattle’s rush-hour traffic, keeping an eye on their blood pressure. They did three trips: two with normal unfiltered air like most people experience, and one with high-quality HEPA filters blocking 86% of pollution. The participants didn’t know which drive had cleaner air.
Bad air
Breathing in unfiltered air made their blood pressure shoot up by more than 4.50 mm Hg (that’s millimeters of mercury). This increase happened quickly, hitting its highest point about an hour into the drive and staying up for at least 24 hours. They didn’t check beyond that 24-hour mark.
This jump in blood pressure is similar to what you’d get from a diet with too much salt. It shows how even routine drives in polluted areas can mess with our bodies.
“We know that modest increases in blood pressure like this, on a population level, are associated with a significant increase in cardiovascular disease,” the researchers explain. “There is a growing understanding that air pollution contributes to heart problems. The idea that roadway air pollution at relatively low levels can affect blood pressure this much is an important piece of the puzzle we’re trying to solve.”
Less understood
The results also make us wonder about ultrafine particles, a type of pollutant that isn’t regulated much and isn’t well understood. These particles are tiny—less than 100 nanometers in diameter, so small you can’t see them.
Air pollution from traffic has a lot of these ultrafine particles. In the research, the unfiltered air had a bunch of them, even though the overall pollution level, measured by fine particles (PM2.5), was pretty low. It’s like having an Air Quality Index (AQI) of 36.
“Ultrafine particles are the pollutant that were most effectively filtered in our experiment—in other words, where the levels are most dramatically high on the road and low in the filtered environment,” the authors continue. “So, the hint is that ultrafines may be especially important [for blood pressure]. To actually prove that requires further research, but this study provides a very strong clue as to what’s going on.”
